Cleaning of rollers in printing presses

ABSTRACT

The invention concerns a process for the cleaning of components of rollers that are involved in the printing process. The cleaning process involves supplying solvents to these rollers that remain in the printing machine while being cleaned. The cleaning of components of the rollers that are involved in the printing process takes place by a process in which first the printing ink is removed from the blade chamber and the blade chamber is filled with solvent. During the cleaning an active connection is maintained between the blade chamber and the uncleaned components of the rollers that are involved in the printing process. This active connection does not interfere with the transfer of the solvent. The rollers rotate during the cleaning process so that solvent is transferred from the blade chamber onto the uncleaned components of the rollers that are involved in the printing process. When the solvent arrives on the roller components the printing ink is diluted there and/or dried printing ink is dissolved and are transported back into the blade chamber by the rotation of the rollers.

The invention concerns a process for cleaning the components of rollersthat are involved in the printing process. The cleaning process involvessupplying solvents to these rollers that remain in the printing machinewhile being cleaned.

The printing of a printing substrate in a flexographic printing machinetakes place by a process in which the printing substrate is led on acylinder and a first roller that is provided with printing plates andthat applies the printing ink carried by the printing plate on theprinting substrate. The printing ink required for this is taken out byone or several rollers from a blade chamber that serves as an inkreservoir and transferred onto the printing plates of the print roller.

In accordance with a printing process of such type it is necessary toclean the components of the different rollers e.g. the printing platesprovided on a print roller. The cleaning process is important to preventthe drying and adhesion of the remaining printing ink. The process forremoving firmly adhesive printing ink involves considerable expenditure.The mechanical effects during the cleaning of the components of rollerswith adhesive printing ink frequently leads to damages of the componentsof the rollers.

The patent specification EP 0 742 756 B1 states a process for cleaningof printing plates. In this process small sub areas of the components ofthe rollers are cleaned one after another. A device for theimplementation of the cleaning process contains a nozzle that contains amixing chamber in which a fluid is prepared by mixing pressurized airand a solvent. The nozzle sprays the fluid in the direction of theprinting roller whereby dust, fibers and other particles are detachedfrom the printing plate. Additionally the device contains a suction pipethat sucks off the fluid and also dust, fibers and other particles fromthe printing plate.

One problem of the device required for the implementation of saidcleaning process is the required space inside the printing machine. In aflexographic printing machine that e.g. prints with 8 different inkssimultaneously, the printing rollers are narrowly adjacent such thatthere is no sufficient space for a device of such kind.

Therefore, the task underlying the present invention is to suggest aprocess for the cleaning of the printing plates that requires noadditional device to be integrated into the inking unit.

This task is solved by a process for the cleaning of printing plateswhereby first the printing ink is removed from the blade chamber and theblade chamber is filled with solvent. During the cleaning an activeconnection (mechanical linkage) is maintained between the blade chamberand the roller components that are involved in the printing process andrequire cleaning. This active connection does not interfere with thetransfer of the solvent. The rollers rotate during the cleaning processso that the solvent is transferred from the blade chamber onto theuncleaned components of the rollers that are involved in the printingprocess. When the solvent reaches the roller components, printing ink isdiluted and/or dried printing ink is dissolved. This dissolved printingink is then transported back to the blade chamber by the rotation of therollers.

The particular advantage of this process is that for the cleaning of thecomponents of the rollers that are involved in the printing process,only those components of an inking unit are used that are also necessaryfor the printing operation. As opposed to the printing operation inwhich the roller that is in contact with the blade chamber is suppliedwith printing ink, which the roller delivers to another roller, in thecleaning operation the roller that is in contact with the blade chambercollects printing ink from the other roller. The printing ink is thenwashed off by the solvent in the blade chamber by the roller that is incontact with the blade chamber.

It is preferable to first clean the roller that is in direct connectionwith the blade chamber while no other roller is in contact with thisroller (the roller that is in direct contact with the blade chamber).After cleaning one roller, the next adjacent roller is again broughtinto connection with the previously cleaned roller, whereby again thecontact to the next adjoining and not yet cleaned roller is interrupted.In this manner the components of all the rollers that are involved inthe printing process can be cleaned successively and effectively.

It is advantageous if the solvent is circulated inside the bladechamber. This can happen in a closed circulation in which only one pumpis connected between discharge and feed lines. In a preferential designform however one part of the solvent is continuously sucked off via thedischarge line from the blade chamber and led into e.g. a dirt tank. Thequantity taken out is replaced by non-polluted solvent that is suppliedto the blade chamber via the feed lines.

It is useful if the roller that is in direct connection with the bladechamber is kept in constant rotation so that its individual surfaceareas are periodically brought into contact with the solvent in order tocompletely wash off the printing ink from the roller.

It is particularly advantageous if all the rollers that are inconnection with one another rotate with the same circumferential speedsin order to avoid material wear of the components of the rollers.

In order to ensure that the printing ink from one roller is completelycollected by another roller, the rollers that are in connection witheach other are arranged closer to one another compared to theirarrangement during the printing operation.

Since in case of a closer arrangement of the rollers the individualpoints on the printing plates can be exposed to a milling movement,there exists the risk that the areas around the points of the printingplates are not cleaned completely. For a thorough cleaning it is usefulto reverse the rotational direction of the rollers at least once.

For the automatic implementation of the described process a preferentialdesign form of the invention provides the printing machine with controlequipment that also allows manual intervention during the cleaningoperation if necessary.

The invention is described more elaborately on the basis of the figures.The individual figures illustrate:

FIG. 1 Inking unit of a flexographic printing machine in the printingoperation.

FIG. 2 Inking unit of a flexographic printing machine in the cleaningoperation.

In the printing operation of an inking unit 1 in a centralcylinder-printing machine in accordance with FIG. 1 the printing inkarrives in the desired format on the printing substrate, in that it isfirst supplied via the feed line 9 from an ink kit to the blade chamber2. The anilox roller 3 that rotates in the direction of the arrow Ctakes over one part of the printing ink. For this purpose the surface ofthe anilox roller has small depressions (not illustrated) the so-calledsaucers into which the printing ink arrives. The saucers that come intocontact with the printing plate 8 release their printing ink there. Theprinting plate 8 is applied on the printing roller 4 and is moved by arotation of the printing roller 4 in the direction of the arrow B to theprinting substrate 5. There the printing plate 8 dispenses the printingink that is clinging to it onto the printing substrate 5. For thepurpose of the complete ink transfer the printing substrate 5 that isfed via a deflecting roller 7 runs over the impression cylinder 6 thatrotates in the direction of the arrow A.

FIG. 2 illustrates the same inking unit 1 in the cleaning operation. Forthe cleaning of the printing plate 8 the printing roller 4 can bepressed down (as displayed) by the impression cylinder 6. The rotationaldirections B, C of the printing roller 4 and of the anilox roller 3 canbe reversed in comparison with the printing operation. The cleaningprocess starts by removing the ink from the blade chamber 2.Subsequently the blade chamber 2 is filled with solvent via the feedline 9. In order to enable the solvent to take up as much of printingink as possible from the anilox roller, the solvent is circulated byconstantly removing it from the blade chamber 2 via the discharge line10 and feeding this and/or new solvent to the blade chamber 2 via thefeed line 9. If the rotation of the print roller 4 is stopped all areasof the printing plate 8 come into contact with the anilox roller 3within one rotation whereby the printing plate 8 releases a part of theprinting ink clinging to it. In order to ensure a good ink transfer, theanilox roller 3 can be arranged closer to the print roller 4 as can beseen in FIG. 2. Due to the earlier flow of the saucers through the bladechamber 2, the latter are completely or partly filled with solvent, thusfurther improving the ink transfer. The saucers of the anilox roller 3that are supplied with printing ink are cleaned by the circulation ofnew solvent inside the blade chamber 2. The cleaning operation of theinking unit 1 is maintained till there is no more printing ink on theprinting plate 8. List of reference symbols 1 Inking unit 2 Bladechamber 3 Anilox roller 4 Print roller 5 Printing substrate 6 Impressioncylinder 7 Deflecting roller 8 Printing plate 9 Feed line 10  Dischargeline A Rotational direction of the impression cylinder B Rotationaldirection of the printing roller C Rotating direction of the aniloxcylinder

1. Process for the cleaning of components (8) of rollers that areinvolved in the printing process. The cleaning process involvessupplying solvents to these rollers that remain in the printing machinewhile being cleaned. The process in accordance with the presentinvention is characterized by the fact that the printing ink is removedfrom the blade chamber (2) and the blade chamber (2) is filled withsolvent and that during the cleaning an active connection is maintainedbetween the blade chamber (2) and the uncleaned components (8) of therollers (3, 4) that are involved in the printing process. This activeconnection does not interfere with the transfer of the solvent. Theprocess in accordance with the invention is also characterized by thefact that the rollers (3, 4) rotate during the cleaning process so thatsolvent is transferred from the blade chamber (2) onto the uncleanedcomponents of the rollers (3, 4) that are involved in the printingprocess. When the solvent arrives on the components to be cleaned, inkis diluted and/or dried residual ink is dissolved and transported backto the blade chamber by the rotation of the rollers (3, 4).
 2. Processin accordance with claim 1 characterized by the fact that components (8)of several rollers (3, 4) are cleaned, whereby first the roller (3) thatis in direct contact with the blade chamber is cleaned, while the activeconnection with this or the other rollers (4) is interrupted and thenthe active connection between each cleaned roller (3) and the nextadjoining roller (4) is reestablished successively.
 3. Process inaccordance with claim 1 characterized by the fact that the solvent iscontinuously circulated inside the blade chamber (2).
 4. Process inaccordance with claim 3 characterized by the fact that a part of thesolvent is sucked off via a discharge line (9) from the blade chamber(2) and that a part of the discharged and/or non-contaminated solvent isfed to the blade chamber (2) via a feed line (10).
 5. Process inaccordance with claim 1 characterized by the fact that the roller (3)that is in direct connection with the blade chamber (2) is maintained inconstant rotation for its cleaning and in constant contact with thesolvent contained in the blade chamber (2).
 6. Process in accordancewith claim 1 characterized by the fact that the rollers (3, 4) betweenwhich an active connection exists, rotate with the same circumferentialspeeds.
 7. Process in accordance with claim 1 characterized by the factthat in the cleaning operation the rollers (3, 4) between which anactive connection exists, are arranged closer to each other incomparison to their arrangement in the printing operation.
 8. Process inaccordance with claim 1 characterized by the fact that the rotationaldirection of the rollers (3, 4) is reversed at least once.
 9. Controlequipment for a printing machine for the automatic implementation of aprocess in accordance with claim 1.